Preparation of n-alkyl diethanolamines



Patented Oct. 19, 1948 mummies-ogg ggnwmrmon William fqresham, wilmingjzonfbel assignor to I. du Pont de Ne moii'rsp C iiiiipafiyjwil- 'mingt'on; Del.,' a cor dratioifor Delaware No Drawing. Application-Jiilyfi, 1944,

1 Serial No. 5443137 Glaims. (c1. 260 584) This invntiiin relates tot'he'a lkylation of organic compounds and moreparticularly the in- Vention' felates to the N-alliylation of dialkanola'ni ines and to'there" "ltirig alkylated products.

An 'dbjCfbfffi p sht irivention is to provide a process for the'alkylationof dialkanolamines by the reaction of" sometimes with an alkyl sulfate. A further object'isto provide suitablereaction conditions for conducting these alkylation reactions. Yet another object is to provide a process in which N-alkylation of dialkanolamine is effected with the formation of substantially no alkyl'ated products. Other objects and advantages of the invention will hereinafter appear.

The process may be generically illustrated by this equation:

2 (HOR) 2NH+ (R1) 2SO4+Na2CO3- 2 (HOR) 2NR1 +Na2SO4+Hz0 CO2 in which R and R1 are hydrocarbon groups.

The process is conducted in accord with the invention by introducing a dialkan-olamine, an alkali metal or an alkaline earth metal carbonate and an alkyl sulfate into a reaction vessel and conducting the reaction therein at a temperature between 20 and 150 C. for a period of time in the order of from 1 to 4 hours. The alkali metal and alkaline earth metal carbonates tend to decompose the alkyl sulfates. is minimized in accord with a preferred embodiment of the invention by the simultaneous introduction of two streams into the dialkanolamine, the dialkyl sulfate constituting one stream and an aqueous solution of the carbonate the other stream, a slight molar excess of the carbonate being used over that necessary to convert the sulfate ions liberated to sodium sulfate.

The alkanolamines that may be alkylated in accord with the invention include, more particularly, the symmetrical dialkanolamines such, for example, as diethanolamine, dipropanolamine, dibu'tanolamine; and the higher dialkanolamines, as well as the unsymmetrical alkyl alkanolamines, such for example as, methyl ethanolamine, ethyl ethanolamine, methyl propanolamine, etc.

The prior art does not teach how to alkylate hydroxyamine without substitution on the hydroxyl groups. In contradistinction to the processes of the art the dialkanolamines are alkylated in accord with this invention in the presence of an alkali metal carbonate and they are alkylated almost exclusively on the nitrogen group with substantially no alkylation on the oxygen of the hydroxyl groups. The alkylating agent should This undesirable action 2 be present preferably in; amounts from 0.5to 15 moles thereof per mole of the amine. l I Moredet-ailed practice of the invention is illustrated by the accompanying examples of preferred embodiments of the invention in whichparts are by weight unless otherwise indicated. A; v

a Example 1 .A vessel was partially filled with 52.5 parts (0.5 mole) of diethanolamine (HOCI-IzCHz) 2NH into which parts (0.42 mole) of diethyl sulfate was gradually added with agitation over a period of about 2 hours at a temperature of 25 to 35 C. The resulting mixture was processed for an additional period at room temperature for 8 hours. A 61% yield of N-ethyl diethanolamine (HOCH2CH2)NC2H5 was recovered by distillation. The low yield resulted from the presence of large amounts of the O-ethyl derivatives.

Example 2.--The process of Example 1 was repeated with 105 parts (1 mole) of diethanolamine, 38.5 parts (0.25 mole) of diethyl sulfate, and 31 parts (0.25 mole) of Na2CO3.H2O in 30 parts (1.65 moles) of water, the diethyl sulfate and the aqueous solution of sodium carbonate being added as separate streams. The diethyl sulfate and sodium carbonate in water was gradually added with agitation in 0.5 and 1.5 hours respectively at 20 to 33 C. and 33 to 92 C. The resulting mixture was then processed for 2 hours at about 92 C. A 90.5% yield of N-ethyldiethanolamine was obtained. No O-ethylated derivatives were formed.

Example 3.The process of Example 2 was repeated using 52.5 parts of diethanolamine, 38.5 parts of diethyl sulfate, 31 parts of Na2C-O3.H2O in parts of water. The sulfate and aqueous solution of the carbonate were added in 0.66 hours and 1.5 hours respectively at 28 to 33 C. and 33 to 92 C. The processing was continued for 2 hours at 92 C. A 91.5% yield of N-ethyl diethanolamine with no O-ethylation was obtained.

Example 4.--This example illustrates the use of a hydroxide instead of a carbonate. It will be noted that O-ethylation is not inhibited.

The process of Example 2 was repeated with 78.75 parts (0.75 mole) of diethanolamine, 38.5 parts (0.25 mole) of diethyl sulfate, 20 parts (0.50 mole) of sodium hydroxide and 15 parts of water. The sulfate and hydroxide were added at a temperature of 29 to 34 C. Appreciable amounts of the O-ethylation products were obtained.

The synthesis may, if desired. be carried out b way of a continuous process as distinguished from a batchwise process. By such a process the dialkanolamlne together with the alkylating agent with an alkali metal carbonate are introduced continuously with agitation into a reaction zone while the N-alkyl dialkan-ol amine is continuously withdrawn.

I claim:

1. In a process for the preparation of an N- ethyl diethanolamine substantially free from O- alkylated derivatives the step which comprises subjecting a diethanolamine to a reaction with di;

ethyl sulfate in the presence of an aqueous solu tion of sodium carbonate at a temperature between 20 and 150 C. the decomposition of the alkyl sulfate being minimized by the use of a slight molar excess of the sodium carbonate over that necessary to convert the sulfate ions liber-. ated to sodium sulfate.

2. In a process for the preparation of-N-eth 1 diethanolamine substantially free from O-alkylated derivatives the step which comprise subjecting 0.5 mole of diethanolamine, 0.25 mole of diethyl sulfate, 0.25 mole of NazCOaHzO and 1.65 moles of Water to a reaction at a temperature of about 92 C.

3. In a process for the preparation of N-ethyl diethanolamine substantially free from O-alkylated derivatives the step which comprises gradually introducing 0.25 mole of diethyl sulfate as one stream and 0.25 mole of Na2CO3.I-I2O and 1.65

4 moles of water as another stream into 0.5 mole of diethanolamine and conducting the reaction at a temperature of not more than about 92 C.

4. In a process for the preparation of N-alkyl diethanolamines substantially free from O-alkylated derivatives the steps which comprise simultaneously introducing two streams of reactants into a reaction zone containing diethanolamine maintained at a temperature between 20 and 0:, one stream consisting of a dialkyl sulfate, the other an aqueous solution of sodium carbonate, the decomposition of the alkyl sulfate being minimized by the use of a slight molar excess of the sodium carbonate over that necessary to convert thesulfate ions liberated to sodium sulfate.

' WILLIAM F. GRESHAM.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS 

